Accreting black holes emit copious radiation, eject outflows, and enrich the Universe with heavy elements. Particularly interesting and challenging are luminous accretion flows, which are easy to observe because they are bright but challenging to model because the radiation cools them into thin, difficult-to-resolve disks. The numerical challenge becomes extreme in the typical but relatively unexplored case of tilted accretion, where the black hole and accretion midplanes are misaligned. For the past 40 years, the standard expectation has been that the inner regions of tilted thin disks align with the black hole midplane; tantalizingly, general relativistic simulations have shown no such alignment. Facilitated by Blue Waters, we developed a GPU-accelerated adaptive mesh refinement (AMR) general relativistic MHD code, H-AMR, and carried out the simulations of thinnest tilted disks to date. We find that the inner regions of the disk not only align with the black hole but also break off from the outer, misaligned parts of the disk, resulting in wide range of theoretical and observational consequences.
